Researcher:
Çivitçi, Fehmi

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Fehmi

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Çivitçi

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Çivitçi, Fehmi

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2014 - 20183

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Researcher Of Publications: search.filters.isAuthorOfPublication.3c556792-bcbc-4e7f-b26a-43e6abe74991

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    Simultaneous two-wavelength readout for thermo-mechanical MEMS detectors
    (IEEE, 2014) Ferhanoğlu, Onur; Torun, Hamdi; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Adiyan, Ulaş; Çivitçi, Fehmi; Erarslan, Refik Burak; Ürey, Hakan; PhD Student; Researcher; Other; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; N/A; N/A; College of Engineering; N/A; 194282; N/A; 8579
    We proposed a novel two-wavelength optical readout for grating based thenno-mechanical MEMS arrays by using two color LEDS butt-coupled to a multi-mode fiber, which provides spatial auto-registration of two different color images on a single camera. The -1st diffraction orders of the different colors are simultaneously monitored with different channels (R and G) of the RGB camera. The sensitivity of the MEMS array is improved by using the channel data with higher sensitivity for each MEMS detector under a thermal load.
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    A 35--μm pitch IR thermo-mechanical MEMS sensor with AC-coupled optical readout
    (IEEE-Inst Electrical Electronics Engineers Inc, 2015) Ferhanoğlu, Onur; Torun, Hamdi; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Adiyan, Ulaş; Çivitçi, Fehmi; Ürey, Hakan; PhD Student; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; 194282; 8579
    A thermo-mechanical MEMS detector with 35-mu m pixel pitch is designed, fabricated, and characterized. This fabricated design has one of the smallest pixel sizes among the IR thermo-mechanical MEMS sensors in the literature. The working principle of the MEMS detector is based on the bimaterial effect that creates a deflection when exposed to IR radiation in the 812-mu m waveband. The nanometer level out of plane mechanical motion is observed in response to IR heating of the pixel, which is detected by a diffraction grating-based optical readout. Performance of MEMS sensor arrays with optical readout have been limited by a large DC bias that accompanies a small AC signal. We developed a novel optical setup to reduce the DC term and the related noise using an AC-coupled detection scheme. Detailed noise characterization of the pixel and the readout system is reported in this paper. The noise equivalent temperature difference of our detector is measured as 216 mK using f/0.86 lens with the AC-coupled optical readout. Finally, we obtained a thermal image using a single MEMS pixel combined with a scanning configuration. Despite the reduced pixel size, the measured noise levels are comparable to the state-of-the-art thermo-mechanical IR sensors.
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    PublicationOpen Access
    Scanning fiber microdisplay: design, implementation, and comparison to MEMS mirror-based scanning displays
    (Optical Society of America (OSA), 2018) Ferhanoğu, Onur; Department of Electrical and Electronics Engineering; Khayatzadeh, Ramin; Çivitçi, Fehmi; Ürey, Hakan; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/A; N/A; 8579
    In this study, we propose a compact, lightweight scanning fiber microdisplay towards virtual and augmented reality applications. Our design that is tailored as a head-worn-display simply consists of a four-quadrant piezoelectric tube actuator through which a fiber optics cable is extended and actuated, and a reflective (or semi-reflective) ellipsoidal surface that relays the moving tip of the fiber onto the viewer's retina. The proposed display, offers significant advantages in terms of architectural simplicity, form-factor, fabrication complexity and cost over other fiber scanner and MEMS mirror counterparts towards practical realization. We demonstrate the display of various patterns with similar to VGA resolution and further provide analytical formulas for mechanical and optical constraints to compare the performance of the proposed scanning fiber microdisplay with that of MEMS mirror-based microdisplays. Also we discuss the road steps towards improving the performance of the proposed scanning fiber microdisplay to high-definition video formats (such as HD1440), which is beyond what has been achieved by MEMS mirror based laser scanning displays.